Commodity And Other Derivative Contractual Assets And Liabilities (Concentrations of Credit Risk Related to Derivatives) (Details) - Texas Competitive Electric Holdings Company LLC - Credit Risk Contract [Member] $ in Millions	9 Months Ended
	Sep. 30, 2015 USD ($)
Derivative [Line Items]
Total credit risk exposure to all counterparties related to derivative contracts	$ 506
Net exposure to those counterparties after taking into effect master netting arrangements, setoff provisions and collateral	237
Largest net Exposure to single counterparty	$ 75
Credit risk exposure to banking and financial sector percentage	74.00%
Net exposure to banking and financial sector percentage	52.00%